1. Field of the Invention
The present invention relates to a sheet feeding device, and an image forming apparatus comprising a sheet feeding device.
2. Description of the Related Art
Conventionally, various designs of sheet feeding device which separates one sheet from the loaded sheets and delivers the sheet are proposed and put in practical use. For example, a conventional sheet feeding device of widely used type includes a sheet feeding member and a friction pad, the friction pad being depressed on the peripheral surface of the sheet feeding member.
In the sheet feeding device of the above type, the uppermost sheet among the sheets loaded on the sheet loading member is depressed on the peripheral surface of the sheet feeding member, delivered through rotation of the sheet feeding member, and separated from the other loaded sheets when the uppermost sheet passes by between the sheet feeding member and the friction pad, so that only the uppermost sheet is delivered.
In order to separate the sheet one by one certainly, it is necessary for the sheet feeding device of the above type to set a coefficient of friction of the friction pad relative to the sheet at a sufficiently large value. However, when the coefficient of friction of the friction pad is enlarged in this way, the sheet which passes through the area between the friction pad and the sheet feeding member is subjected to stick slipping, and there is a possibility that abnormal noise takes place.
Japanese Laid-Open Patent Application No. 2003-026348 discloses a sheet feeding device which is adapted for resolving the above problem.
In the sheet feeding device disclosed in Japanese Laid-Open Patent Application No. 2003-026348, the sheet loading member, the sheet feeding member and the inclination member are provided. The sheet from the sheets loaded on the sheet loading member is depressed to the peripheral surface of the uppermost surface of the sheet feeding member. The sheet feeding member serves to deliver the sheet through rotation of the peripheral surface. The inclination member includes a depression portion and an inclined surface. The sheet is depressed to the peripheral surface of the uppermost layer of the sheet feeding member by the depression portion of the inclination member. The leading edge of the sheet delivered is brought into contact with the inclined surface of the inclination member.
According to the sheet feeding device of this type, it is not necessary to enlarge the coefficient of friction of the depression portion of the inclination member relative to the sheet as in the above-mentioned friction pad. The sheet is pinched by the depression portion of the inclination member and the sheet feeding member and delivered through rotation of the sheet feeding member. Thus, it is possible to prevent the occurrence of stick slipping and the occurrence of abnormal noise effectively.
However, consideration as to the characteristics of the uppermost surface of the sheet feeding member in the conventional device is not taken adequately. It is likely that the sheet feeding member comes to slip to the sheet at a comparatively early stage, and there is a possibility that the sheet feeding member is not capable of delivering the sheet correctly due to the slipping.